1. Field of the Invention
This invention relates generally to analog-to-digital converters, and is more particularly directed to an analog-to-digital converter which can provide a digital signal having increased accuracy, but without incurring a concomitant increase in the bit number thereof.
2. Description of the Prior Art
When a color video signal, for example, a composite color video signal according to the NTSC system, is digitized, a sampling frequency of 4 f.sub.sc is typically used (where f.sub.sc is the frequency of the color subcarrier) and each sample is converted to a word or byte of eight bits. When the accuracy of a reproduced picture derived from the digital video signal is inadequate, it is possible to increase the sampling frequency, or to convert each sample into nine-bit bytes. While these approaches can provide a digital video signal with reduced quantizing error and increased accuracy, they require a complete change of equipment, both in the analog-to-digital converter and also in the associated digital-to-analog converter.
In the case of digital video recording, it is desirable to provide recorded digital signals such that any quantizing errors are reduced, but no circuit changes are required in the digital-to-analog converter of the associated reproducing apparatus.